A variety of medical devices for delivering a therapy and/or monitoring a physiological condition have been used clinically or proposed for clinical use in patients. Examples include medical devices that deliver therapy to and/or monitor conditions associated with the heart, muscle, nerve, brain, stomach or other organs or tissues. In some medical devices, one or more elongated electrical leads are utilized that carry electrodes for one or both sensing intrinsic electrical signals within the patient and delivering therapeutic electrical signals to certain organs or tissues, and/or other sensors for sensing physiological parameters of a patient. In other medical devices, the electrodes and/or sensors are formed on or located within a housing of the device, rather than being positioned on an electrode lead.
During detection of cardiac events, the observed electrical signal of cardiac activity can be corrupted by noise and/or artifacts from a large variety of sources. The highly constrained computational capability of these devices limits the available options for noise recognition and rejection algorithms. Therefore, what is needed is a method and apparatus for reducing the effect of noise during detection of a cardiac event and that minimizes computational demand on the medical device.